SPDK has had its share of detractors here on news.yc [0], especially with io_uring around the block [1]. It'd be interesting to see the improvements to these io-centric applications once they move to io_uring [2], which, in a way, like RocksDB, is sponsored by Facebook [3].
[0] https://news.ycombinator.com/item?id=10511960
[1] https://news.ycombinator.com/item?id=22266503